Adaptive algorithms for interrogating the viewable scene of an automotive radar

ABSTRACT

A radar system in an autonomous vehicle may be operated in various modes and with various configurations. In one example, the radar system determines a target range for further interrogation. The target range may be determined based on the radar system transmitting a first electromagnetic radiation signal and receiving a first reflected electromagnetic signal radiation signal. After the radar system determines a target range, it transmits a second electromagnetic radiation signal. Additionally, the radar system receives a reflected electromagnetic signal radiation based on the transmission. After receiving the reflected signal, the radar system can process the reflected signal to only have components associated with the target range. The processing of the reflected signal may create a processed signal. Finally, the radar system may determine at least one parameter of a target object based on the processed signal.

CROSS REFERENCE TO RELATED APPLICATION

This application is continuation-in-part of and claims priority to U.S.patent application Ser. No. 13/778,722, filed Feb. 27, 2013, now U.S.Pat. No. 9,261,590, the disclosure of which is hereby incorporated byreference.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

A vehicle could be any wheeled, powered vehicle and may include a car,truck, motorcycle, bus, etc. Vehicles can be utilized for various taskssuch as transportation of people and goods, as well as many other uses.

Some vehicles may be partially or fully autonomous. For instance, when avehicle is in an autonomous mode, some or all of the driving aspects ofvehicle operation can be handled by a vehicle control system. In suchcases, computing devices located onboard and/or in a server networkcould be operable to carry out functions such as planning a drivingroute, sensing aspects of the vehicle, sensing the environment of thevehicle, and controlling drive components such as steering, throttle,and brake. Thus, autonomous vehicles may reduce or eliminate the needfor human interaction in various aspects of vehicle operation.

SUMMARY

In order to aid the vehicle control system, an autonomous vehicle mayinclude a radar system. The radar system may be operated in variousmodes and with various configurations based on the intended use andoperating conditions.

In a first embodiment, a method for operating a radar system isprovided. The radar system determines a target range. The target rangemay be determined based on the radar system transmitting a firstelectromagnetic radiation signal and receiving a first reflectedelectromagnetic signal radiation signal. The radar system transmits asecond electromagnetic radiation signal. Additionally, the radar systemreceives a reflected electromagnetic signal radiation based on thetransmitted second electromagnetic radiation signal. After receiving thereflected signal, the radar system can process the reflected signal toonly have components associated with the target range. The processing ofthe reflected signal may create a processed signal. Finally, the radarsystem may determine at least one parameter of a target object based onthe processed signal.

In a second embodiment, a radar system is provided. The radar system isconfigured with an antenna system configured to transmit and receiveelectromagnetic radiation. Additionally, the radar system has atransceiver. The transceiver is configured to cause the antenna systemto (i) transmit a first electromagnetic radiation signal and (ii)receive a first reflected electromagnetic signal radiation based on thefirst transmitted electromagnetic radiation signal. Additionally, thetransceiver causes the antenna system to (i) transmit a secondelectromagnetic radiation signal and (ii) receive a second reflectedelectromagnetic signal radiation based on the second transmittedelectromagnetic radiation signal. Moreover, the radar system includes aprocessing unit. The processing unit is configured to (i) determine atarget range based on the first reflected electromagnetic radiationsignal and (ii) process the received second reflected electromagneticsignal to only have components associated with the target range toprovide a processed signal. Furthermore, the processing unit is alsoconfigured to determine at least one parameter of the target objectbased on the processed signal.

In a third embodiment, an article of manufacture including anon-transitory computer-readable medium having program instructionsstored thereon is provided. When the program instructions are executedby a processor in a radar system, cause the radar system to performoperations. The operations include determining a target range andtransmitting a second electromagnetic radiation signal. Additionally,the operations include receiving a reflected electromagnetic signalradiation based on the transmitted electromagnetic radiation signal. Theoperations further include processing the received reflectedelectromagnetic signal to only have components associated with thetarget range to provide a processed signal. Finally, the operationsinclude determining at least one parameter of the target object based onthe processed signal.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating a vehicle, accordingto an example embodiment.

FIG. 2 shows a vehicle, according to an example embodiment.

FIG. 3A is a top view of an autonomous vehicle operating scenario,according to an example embodiment.

FIG. 3B is a top view of an autonomous vehicle operating scenario,according to an example embodiment.

FIG. 3C is a top view of an autonomous vehicle operating scenario,according to an example embodiment.

FIG. 3D is a top view of an autonomous vehicle operating scenario,according to an example embodiment.

FIG. 4 shows a method, according to an example embodiment.

FIG. 5 is a schematic diagram of a computer program product, accordingto an example embodiment.

DETAILED DESCRIPTION

Example methods and systems are described herein. Any example embodimentor feature described herein is not necessarily to be construed aspreferred or advantageous over other embodiments or features. Theexample embodiments described herein are not meant to be limiting. Itwill be readily understood that certain aspects of the disclosed systemsand methods can be arranged and combined in a wide variety of differentconfigurations, all of which are contemplated herein.

Furthermore, the particular arrangements shown in the Figures should notbe viewed as limiting. It should be understood that other embodimentsmight include more or less of each element shown in a given Figure.Further, some of the illustrated elements may be combined or omitted.Yet further, an example embodiment may include elements that are notillustrated in the Figures.

1. Overview

Example embodiments disclosed herein relate to a radar system includinga range dwell mode in an autonomous vehicle. Further, the embodimentsdisclosed herein may also be used to optimize the radar system based ona target region of interest.

The radar system of the autonomous vehicle may feature a plurality ofantennas. Each antenna may be configured to (i) transmit electromagneticsignals, (ii) receive electromagnetic signals, or (iii) both transmitand receive electromagnetic signals. The antennas may form an array ofantenna elements. The array may be able to steer a beam formed by thetransmitted electromagnetic signals. Additionally, the array may aid indetecting the range from which electromagnetic signals are received.

Radar systems transmit an electromagnetic signal and receive reflectionsof the electromagnetic signal from various objects within a field ofview of the radar system. Various objects will reflect theelectromagnetic signal differently. For example, larger objects mayreflect a larger amount of the electromagnetic signal. Smaller objectsmay reflect less of the electromagnetic signal. However, in someinstances, a large object may cause a large enough reflection that someof the reflections from smaller objects may be overwhelmed. Thus, it maybe desirable to minimize the impact of the reflections from largeobjections.

Some conventional radar systems use beam steering to minimize the impactof undesirable reflections. When a radar system uses beam steering, thetransmitted beam may be steered away from the location of theundesirable reflection. Beam steering may also be used to mathematicallyremove signals from undesirable directions in received signals. However,beam steering may not produce desirable results in several situations.For example, if the reflecting object reflects enough signal, even beamsteering may not mitigate the reflections. Further, target objects maybe located near the large reflecting object. Thus, it may not bepossible to steer the beam away from the large reflecting object.

However, by operating the radar in a range dwell mode, the undesiredreflections may be reduced or mitigated. In one embodiment, the radarsystem may identify a range of interest. The radar system may onlyprocess signals corresponding to the range of interest. In anotherembodiment, the radar system may identify an undesired range. The radarsystem may operate by not processing signals corresponding to theundesired range. Thus, the reflections from undesirable objects may beremoved from the radar system based on the range of the target objectsand the undesirable objects.

Within the context of the disclosure, the vehicle could be operable invarious modes of operation. Depending on the embodiment, such modes ofoperation could include manual, semi-autonomous, and autonomous modes.In particular, the autonomous mode may provide driving operation withlittle or no user interaction. Manual and semi-autonomous modes ofoperation could provide for driving operations with a greater degree ofuser interaction.

Additionally, the vehicle could be operated in a safety mode. The safetymode could represent an autonomous, semi-autonomous, or manual mode inwhich the vehicle may be controlled to operate in a safe fashion. Suchsafety modes of operation could include the vehicle autonomously pullingover to the side of a road and/or the vehicle returning some or alloperational control of the vehicle to a driver or another controlsystem.

Some methods disclosed herein could be carried out in part or in full bya vehicle configured to operate in an autonomous mode with or withoutexternal interaction (e.g., such as from a user of the vehicle). In onesuch example, the vehicle may feature a radar system. The radar systemmay be used for several different purposes. The navigation system of thevehicle may use the radar to locate objects in the path of the vehicle.Additionally, the radar may be used to locate and/or help identify otherobjects near the vehicle.

During the operation of the radar, at least one antenna in the radarsystem may transmit a radio signal. The transmitted radio signal maypropagate away from the antenna and may be reflected by various objects.The reflected radio signals may be received by at least one antenna inthe radar system. The radar system may additionally have a processingunit configured to process the received reflected radio signals. Basedon the received reflected radio signals, the processing unit may be ableto locate the objects that caused the reflections. The processing unitmay be able to calculate an angle and a distance to each object thatreflected the radio signal.

In some embodiments, the radar may be configured with multiple antennas.By having multiple antennas, the radar system may have more control overthe radar beam. For example, the radar system may be able to adjust thebeam width and/or direction. Having more control over the radar beamallows the radar system to more accurately locate objects. In oneembodiment, a plurality of antennas may be arranged in an array. Theantenna elements in the array may have an even spacing between elements(i.e. the distance between each element is the same) or the antenna mayhave a non-even spacing. Additionally, the array may be a linear array,a two dimensional array, three dimensional array, conformal array, orother array configuration.

The radar system may also include a computer processor. The processormay be configured to calculate some parameters of objects within thefield of view of the radar system either before the operation of theradar or during the operation of the radar. For example, in oneembodiment, the processor is configured to calculate the distance (andangle) to various objects in the field of view of the radar. Thedistance may correspond to a time delay and/or a frequency shift withwhich a reflected radio signal returns to the antennas. Additionally,the radar system may be configured to determine whether each reflectingobject is desirable or undesirable. Based on the determination ofdesirable and undesirable objects, the processor may determine a rangeof interest. The range of interest may correspond to a range of distancein which all the desired object are located. The range of interest mayalso correspond to a range of angles in which all the desired object arelocated. Further, the range of interest may correspond to a range ofdistance and angles in which none the undesired object are located.

In some embodiments, the processor may operate the radar system in aFMCW mode after a range of interest is identified. By operating theradar in an FMCW mode, the radar system can remove signals that do notcorrespond to the region of interest. Additionally, in some embodiments,the processor may also steer the radar beam away from undesirabletargets. Thus, the processor may operate in a way to reduce the presenceof undesired signals. By determining a region of interest and furtherinterrogating the region (while removing undesirable information), ahigher quality signal from the region of interest can be obtained.

A server, such as one or more nodes of a server network, couldadditionally (or alternatively) carry out the methods disclosed hereinin part or in full. In an example embodiment, a server or computer mayreceive an indication of an operation mode of the radar system. Suchindications could include any current parameters of the antenna system(e.g., operation frequency, reflected signal information, the on/offstate of each antenna). Further, the server may already know (orreceive) information related to the position of various objects withrespect to the vehicle. Such information could aid in the determinationof the region of interest.

Also disclosed herein are non-transitory computer readable media withstored instructions. The instructions could be executable by a computingdevice to cause the computing device to perform functions similar tothose described in the aforementioned methods.

It is understood that there are many different specific methods andsystems that could be used in an unambiguous angle calculation for theradar system. These specific methods and systems are contemplatedherein, and several example embodiments are described below.

2. Example Systems

Example systems within the scope of the present disclosure will now bedescribed in greater detail. An example system may be implemented in ormay take the form of an automobile. However, an example system may alsobe implemented in or take the form of other vehicles, such as cars,trucks, motorcycles, buses, boats, airplanes, helicopters, lawn mowers,earth movers, boats, snowmobiles, aircraft, recreational vehicles,amusement park vehicles, farm equipment, construction equipment, trams,golf carts, trains, and trolleys. Other vehicles are possible as well.

FIG. 1 is a functional block diagram illustrating a vehicle 100,according to an example embodiment. The vehicle 100 could be configuredto operate fully or partially in an autonomous mode. For example, acomputer system could control the vehicle 100 while in the autonomousmode, and may be operable to transmit a radio signal, receive reflectedradio signals with at least one antenna in the radar system, process thereceived reflected radio signals, locate the objects that caused thereflections, calculate an angle and a distance to each object thatreflected the radio signal, and calculate an unambiguous angleassociated with the angle. While in autonomous mode, the vehicle 100 maybe configured to operate without human interaction.

The vehicle 100 could include various subsystems such as a propulsionsystem 102, a sensor system 104, a control system 106, one or moreperipherals 108, as well as a power supply 110, a computer system 112, adata storage 114, and a user interface 116. The vehicle 100 may includemore or fewer subsystems and each subsystem could include multipleelements. Further, each of the subsystems and elements of vehicle 100could be interconnected. Thus, one or more of the described functions ofthe vehicle 100 may be divided up into additional functional or physicalcomponents, or combined into fewer functional or physical components. Insome further examples, additional functional and/or physical componentsmay be added to the examples illustrated by FIG. 1.

The propulsion system 102 may include components operable to providepowered motion for the vehicle 100. Depending upon the embodiment, thepropulsion system 102 could include an engine/motor 118, an energysource 119, a transmission 120, and wheels/tires 121. The engine/motor118 could be any combination of an internal combustion engine, anelectric motor, steam engine, Stirling engine. Other motors and/orengines are possible. In some embodiments, the engine/motor 118 may beconfigured to convert energy source 119 into mechanical energy. In someembodiments, the propulsion system 102 could include multiple types ofengines and/or motors. For instance, a gas-electric hybrid car couldinclude a gasoline engine and an electric motor. Other examples arepossible.

The energy source 119 could represent a source of energy that may, infull or in part, power the engine/motor 118. Examples of energy sources119 contemplated within the scope of the present disclosure includegasoline, diesel, other petroleum-based fuels, propane, other compressedgas-based fuels, ethanol, solar panels, batteries, and other sources ofelectrical power. The energy source(s) 119 could additionally oralternatively include any combination of fuel tanks, batteries,capacitors, and/or flywheels. The energy source 118 could also provideenergy for other systems of the vehicle 100.

The transmission 120 could include elements that are operable totransmit mechanical power from the engine/motor 118 to the wheels/tires121. The transmission 120 could include a gearbox, a clutch, adifferential, and a drive shaft. Other components of transmission 120are possible. The drive shafts could include one or more axles thatcould be coupled to the one or more wheels/tires 121.

The wheels/tires 121 of vehicle 100 could be configured in variousformats, including a unicycle, bicycle/motorcycle, tricycle, orcar/truck four-wheel format. Other wheel/tire geometries are possible,such as those including six or more wheels. Any combination of thewheels/tires 121 of vehicle 100 may be operable to rotate differentiallywith respect to other wheels/tires 121. The wheels/tires 121 couldrepresent at least one wheel that is fixedly attached to thetransmission 120 and at least one tire coupled to a rim of the wheelthat could make contact with the driving surface. The wheels/tires 121could include any combination of metal and rubber. Other materials arepossible.

The sensor system 104 may include several elements such as a GlobalPositioning System (GPS) 122, an inertial measurement unit (IMU) 124, aradar 126, a laser rangefinder/LIDAR 128, a camera 130, a steeringsensor 123, and a throttle/brake sensor 125. The sensor system 104 couldalso include other sensors, such as those that may monitor internalsystems of the vehicle 100 (e.g., O₂ monitor, fuel gauge, engine oiltemperature, brake wear).

The GPS 122 could include a transceiver operable to provide informationregarding the position of the vehicle 100 with respect to the Earth. TheIMU 124 could include a combination of accelerometers and gyroscopes andcould represent any number of systems that sense position andorientation changes of a body based on inertial acceleration.Additionally, the IMU 124 may be able to detect a pitch and yaw of thevehicle 100. The pitch and yaw may be detected while the vehicle isstationary or in motion.

The radar 126 may represent a system that utilizes radio signals tosense objects, and in some cases their speed and heading, within thelocal environment of the vehicle 100. Additionally, the radar 126 mayhave a plurality of antennas configured to transmit and receive radiosignals. The laser rangefinder/LIDAR 128 could include one or more lasersources, a laser scanner, and one or more detectors, among other systemcomponents. The laser rangefinder/LIDAR 128 could be configured tooperate in a coherent mode (e.g., using heterodyne detection) or in anincoherent detection mode. The camera 130 could include one or moredevices configured to capture a plurality of images of the environmentof the vehicle 100. The camera 130 could be a still camera or a videocamera.

The steering sensor 123 may represent a system that senses the steeringangle of the vehicle 100. In some embodiments, the steering sensor 123may measure the angle of the steering wheel itself. In otherembodiments, the steering sensor 123 may measure an electrical signalrepresentative of the angle of the steering wheel. Still, in furtherembodiments, the steering sensor 123 may measure an angle of the wheelsof the vehicle 100. For instance, an angle of the wheels with respect toa forward axis of the vehicle 100 could be sensed. Additionally, in yetfurther embodiments, the steering sensor 123 may measure a combination(or a subset) of the angle of the steering wheel, electrical signalrepresenting the angle of the steering wheel, and the angle of thewheels of vehicle 100.

The throttle/brake sensor 125 may represent a system that senses theposition of either the throttle position or brake position of thevehicle 100. In some embodiments, separate sensors may measure thethrottle position and brake position. In some embodiments, thethrottle/brake sensor 125 may measure the angle of both the gas pedal(throttle) and brake pedal. In other embodiments, the throttle/brakesensor 125 may measure an electrical signal that could represent, forinstance, an angle of a gas pedal (throttle) and/or an angle of a brakepedal. Still, in further embodiments, the throttle/brake sensor 125 maymeasure an angle of a throttle body of the vehicle 100. The throttlebody may include part of the physical mechanism that provides modulationof the energy source 119 to the engine/motor 118 (e.g., a butterflyvalve or carburetor). Additionally, the throttle/brake sensor 125 maymeasure a pressure of one or more brake pads on a rotor of vehicle 100.In yet further embodiments, the throttle/brake sensor 125 may measure acombination (or a subset) of the angle of the gas pedal (throttle) andbrake pedal, electrical signal representing the angle of the gas pedal(throttle) and brake pedal, the angle of the throttle body, and thepressure that at least one brake pad is applying to a rotor of vehicle100. In other embodiments, the throttle/brake sensor 125 could beconfigured to measure a pressure applied to a pedal of the vehicle, suchas a throttle or brake pedal.

The control system 106 could include various elements include steeringunit 132, throttle 134, brake unit 136, a sensor fusion algorithm 138, acomputer vision system 140, a navigation/pathing system 142, and anobstacle avoidance system 144. The steering unit 132 could represent anycombination of mechanisms that may be operable to adjust the heading ofvehicle 100. The throttle 134 could control, for instance, the operatingspeed of the engine/motor 118 and thus control the speed of the vehicle100. The brake unit 136 could be operable to decelerate the vehicle 100.The brake unit 136 could use friction to slow the wheels/tires 121. Inother embodiments, the brake unit 136 could convert the kinetic energyof the wheels/tires 121 to electric current.

A sensor fusion algorithm 138 could include, for instance, a Kalmanfilter, Bayesian network, or other algorithm that may accept data fromsensor system 104 as input. The sensor fusion algorithm 138 couldprovide various assessments based on the sensor data. Depending upon theembodiment, the assessments could include evaluations of individualobjects and/or features, evaluation of a particular situation, and/orevaluate possible impacts based on the particular situation. Otherassessments are possible.

The computer vision system 140 could include hardware and softwareoperable to process and analyze images in an effort to determineobjects, important environmental features (e.g., stop lights, road wayboundaries, etc.), and obstacles. The computer vision system 140 coulduse object recognition, Structure From Motion (SFM), video tracking, andother algorithms used in computer vision, for instance, to recognizeobjects, map an environment, track objects, estimate the speed ofobjects, etc.

The navigation/pathing system 142 could be configured to determine adriving path for the vehicle 100. The navigation/pathing system 142 mayadditionally update the driving path dynamically while the vehicle 100is in operation. In some embodiments, the navigation/pathing system 142could incorporate data from the sensor fusion algorithm 138, the GPS122, and known maps so as to determine the driving path for vehicle 100.

The obstacle avoidance system 144 could represent a control systemconfigured to evaluate potential obstacles based on sensor data andcontrol the vehicle 100 to avoid or otherwise negotiate the potentialobstacles.

Various peripherals 108 could be included in vehicle 100. For example,peripherals 108 could include a wireless communication system 146, atouchscreen 148, a microphone 150, and/or a speaker 152. The peripherals108 could provide, for instance, means for a user of the vehicle 100 tointeract with the user interface 116. For example, the touchscreen 148could provide information to a user of vehicle 100. The user interface116 could also be operable to accept input from the user via thetouchscreen 148. In other instances, the peripherals 108 may providemeans for the vehicle 100 to communicate with devices within itsenvironment.

In one example, the wireless communication system 146 could beconfigured to wirelessly communicate with one or more devices directlyor via a communication network. For example, wireless communicationsystem 146 could use 3G cellular communication, such as CDMA, EVDO,GSM/GPRS, or 4G cellular communication, such as WiMAX or LTE.Alternatively, wireless communication system 146 could communicate witha wireless local area network (WLAN), for example, using WiFi. In someembodiments, wireless communication system 146 could communicatedirectly with a device, for example, using an infrared link, Bluetooth,or ZigBee. Other wireless protocols, such as various vehicularcommunication systems, are possible within the context of thedisclosure. For example, the wireless communication system 146 couldinclude one or more dedicated short range communications (DSRC) devicesthat could include public and/or private data communications betweenvehicles and/or roadside stations.

The power supply 110 may provide power to various components of vehicle100 and could represent, for example, a rechargeable lithium-ion orlead-acid battery. In an example embodiment, one or more banks of suchbatteries could be configured to provide electrical power. Other powersupply materials and types are possible. Depending upon the embodiment,the power supply 110, and energy source 119 could be integrated into asingle energy source, such as in some all-electric cars.

Many or all of the functions of vehicle 100 could be controlled bycomputer system 112. Computer system 112 may include at least oneprocessor 113 (which could include at least one microprocessor) thatexecutes instructions 115 stored in a non-transitory computer readablemedium, such as the data storage 114. The computer system 112 may alsorepresent a plurality of computing devices that may serve to controlindividual components or subsystems of the vehicle 100 in a distributedfashion.

In some embodiments, data storage 114 may contain instructions 115(e.g., program logic) executable by the processor 113 to execute variousfunctions of vehicle 100, including those described above in connectionwith FIG. 1. Data storage 114 may contain additional instructions aswell, including instructions to transmit data to, receive data from,interact with, and/or control one or more of the propulsion system 102,the sensor system 104, the control system 106, and the peripherals 108.

In addition to the instructions 115, the data storage 114 may store datasuch as roadway maps, path information, among other information. Suchinformation may be used by vehicle 100 and computer system 112 duringthe operation of the vehicle 100 in the autonomous, semi-autonomous,and/or manual modes.

The vehicle 100 may include a user interface 116 for providinginformation to or receiving input from a user of vehicle 100. The userinterface 116 could control or enable control of content and/or thelayout of interactive images that could be displayed on the touchscreen148. Further, the user interface 116 could include one or moreinput/output devices within the set of peripherals 108, such as thewireless communication system 146, the touchscreen 148, the microphone150, and the speaker 152.

The computer system 112 may control the function of the vehicle 100based on inputs received from various subsystems (e.g., propulsionsystem 102, sensor system 104, and control system 106), as well as fromthe user interface 116. For example, the computer system 112 may utilizeinput from the sensor system 104 in order to estimate the outputproduced by the propulsion system 102 and the control system 106.Depending upon the embodiment, the computer system 112 could be operableto monitor many aspects of the vehicle 100 and its subsystems. In someembodiments, the computer system 112 may disable some or all functionsof the vehicle 100 based on signals received from sensor system 104.

The components of vehicle 100 could be configured to work in aninterconnected fashion with other components within or outside theirrespective systems. For instance, in an example embodiment, the camera130 could capture a plurality of images that could represent informationabout a state of an environment of the vehicle 100 operating in anautonomous mode. The state of the environment could include parametersof the road on which the vehicle is operating. For example, the computervision system 140 may be able to recognize the slope (grade) or otherfeatures based on the plurality of images of a roadway. Additionally,the combination of Global Positioning System 122 and the featuresrecognized by the computer vision system 140 may be used with map datastored in the data storage 114 to determine specific road parameters.Further, the radar unit 126 may also provide information about thesurroundings of the vehicle.

In other words, a combination of various sensors (which could be termedinput-indication and output-indication sensors) and the computer system112 could interact to provide an indication of an input provided tocontrol a vehicle or an indication of the surroundings of a vehicle.

The computer system 112 could carry out several determinations based onthe indications received from the input- and output-indication sensors.For example, the computer system 112 could calculate the direction (e.g.angle) and distance (e.g. range) to one or more objects that arereflecting radar signals back to the radar unit 126. Additionally, thecomputer system 112 could calculate a range of interest. The range ofinterest could, for example, correspond to a region where the computersystem 112 has identified one or more targets of interest. Additionallyor additionally, the computer system 112 may identify one or moreundesirable targets. Thus, a range of interest may be calculated so asnot to include undesirable targets.

In some embodiments, the computer system 112 may make a determinationabout various objects based on data that is provided by systems otherthan the radar system. For example, the vehicle may have lasers or otheroptical sensors configured to sense objects in a field of view of thevehicle. The computer system 112 may use the outputs from the varioussensors to determine information about objects in a field of view of thevehicle. The computer system 112 may determine distance and directioninformation to the various objects. The computer system 112 may alsodetermine whether objects are desirable or undesirable based on theoutputs from the various sensors.

Although FIG. 1 shows various components of vehicle 100, i.e., wirelesscommunication system 146, computer system 112, data storage 114, anduser interface 116, as being integrated into the vehicle 100, one ormore of these components could be mounted or associated separately fromthe vehicle 100. For example, data storage 114 could, in part or infull, exist separate from the vehicle 100. Thus, the vehicle 100 couldbe provided in the form of device elements that may be locatedseparately or together. The device elements that make up vehicle 100could be communicatively coupled together in a wired and/or wirelessfashion.

FIG. 2 shows a vehicle 200 that could be similar or identical to vehicle100 described in reference to FIG. 1. Depending on the embodiment,vehicle 200 could include a sensor unit 202, a wireless communicationsystem 204, a radar 206, a laser rangefinder 208, and a camera 210. Theelements of vehicle 200 could include some or all of the elementsdescribed for FIG. 1. Although vehicle 200 is illustrated in FIG. 2 as acar, other embodiments are possible. For instance, the vehicle 200 couldrepresent a truck, a van, a semi-trailer truck, a motorcycle, a golfcart, an off-road vehicle, or a farm vehicle, among other examples.

The sensor unit 202 could include one or more different sensorsconfigured to capture information about an environment of the vehicle200. For example, sensor unit 202 could include any combination ofcameras, radars, LIDARs, range finders, and acoustic sensors. Othertypes of sensors are possible. Depending on the embodiment, the sensorunit 202 could include one or more movable mounts that could be operableto adjust the orientation of one or more sensors in the sensor unit 202.In one embodiment, the movable mount could include a rotating platformthat could scan sensors so as to obtain information from each directionaround the vehicle 200. In another embodiment, the movable mount of thesensor unit 202 could be moveable in a scanning fashion within aparticular range of angles and/or azimuths. The sensor unit 202 could bemounted atop the roof of a car, for instance, however other mountinglocations are possible. Additionally, the sensors of sensor unit 202could be distributed in different locations and need not be collocatedin a single location. Some possible sensor types and mounting locationsinclude radar 206 and laser rangefinder 208.

The wireless communication system 204 could be located as depicted inFIG. 2. Alternatively, the wireless communication system 204 could belocated, fully or in part, elsewhere. The wireless communication system204 may include wireless transmitters and receivers that could beconfigured to communicate with devices external or internal to thevehicle 200. Specifically, the wireless communication system 204 couldinclude transceivers configured to communicate with other vehiclesand/or computing devices, for instance, in a vehicular communicationsystem or a roadway station. Examples of such vehicular communicationsystems include dedicated short range communications (DSRC), radiofrequency identification (RFID), and other proposed communicationstandards directed towards intelligent transport systems.

The camera 210 could be mounted inside a front windshield of the vehicle200. The camera 210 could be configured to capture a plurality of imagesof the environment of the vehicle 200. Specifically, as illustrated, thecamera 210 could capture images from a forward-looking view with respectto the vehicle 200. Other mounting locations and viewing angles ofcamera 210 are possible. The camera 210 could represent one or morevisible light cameras. Alternatively or additionally, camera 210 couldinclude infrared sensing capabilities. The camera 210 could haveassociated optics that could be operable to provide an adjustable fieldof view. Further, the camera 210 could be mounted to vehicle 200 with amovable mount that could be operable to vary a pointing angle of thecamera 210.

FIG. 3A illustrates a scenario 300 involving a vehicle 302 travelingdown a roadway 304. Vehicle 302 could be operating in an autonomousmode. Further, the vehicle 302 may be configured with a radar unit 310.The radar unit 301 may have an associated beam-width 306. In one exampleembodiment, there may be two desirable targets 312 and 314 in front ofthe vehicle 302. A first target 312 and a second target 314 may bewithin the beam-width 306 of the radar unit 310. Additionally, anundesirable target 316 may be within the beam-width 306 of the radarunit 310. For each target identified, a computer located within vehicle302 may determine if each target is desirable or undesirable.Additionally, based on the determination of the desirable andundesirable targets, the computer may determine the range of interest.As shown in FIG. 3A, the range of interest may have a cutoff distanceshown as cutoff limit 320. The radar system will ignore radarreflections that come from a distance further than cutoff limit 320.Thus, the radar system will ignore radar reflections from undesirabletarget 316.

FIG. 3B illustrates a scenario 350 involving a vehicle 302 travelingdown a roadway 304. Similar to FIG. 3A, vehicle 302 could be operatingin an autonomous mode and may be configured with a radar unit 310.Additionally, the radar unit 301 may have an associated beam-width 306.In one example embodiment, there may be two desirable targets 312 and314 in front of the vehicle 302. A first target 312 and a second target314 may be within the beam-width 306 of the radar unit 310. Further, anundesirable target 318 may be within the beam-width 306 of the radarunit 310. Like FIG. 3A, for each target identified, a computer locatedwithin vehicle 302 may determine if each target is desirable orundesirable. Additionally, based on the determination of the desirableand undesirable targets, the computer may determine the range ofinterest. As shown in FIG. 3B, the range of interest may have athreshold distance shown as limit 325. The radar system will ignoreradar reflections that come from a distance less than threshold limit325. Thus, the radar system will ignore radar reflections fromundesirable target 318.

FIG. 3C illustrates a scenario 370 involving a vehicle 302 travelingdown a roadway 304. Similar to FIGS. 3A and 3B, vehicle 302 could beoperating in an autonomous mode and may be configured with a radar unit310. Additionally, the radar unit 301 may have an associated beam-width306. In one example embodiment, there may be two desirable targets 312and 314 in front of the vehicle 302. A first target 312 and a secondtarget 314 may be within the beam-width 306 of the radar unit 310.Further, a first undesirable target 316 and a second undesirable target318 may be within the beam-width 306 of the radar unit 310. Like FIGS.3A and 3B, for each target identified, a computer located within vehicle302 may determine if each target is desirable or undesirable.Additionally, based on the determination of the desirable andundesirable targets, the computer may determine the range of interest.As shown in FIG. 3C, the range of interest may have a cutoff distanceshown as cutoff limit 320 and a threshold distance shown as limit 325.The radar system will ignore radar reflections that come from a distanceless than threshold limit 325 and great than cutoff limit 320. Thus, theradar system will ignore radar reflections from both undesirable target316 and undesirable target 318.

FIG. 3D illustrates a scenario 380 involving a vehicle 302 travelingdown a roadway 304. Similar to previous FIGS. 3A, 3B, and 3C, vehicle302 could be operating in an autonomous mode and may be configured witha radar unit 310. Additionally, the radar unit 301 may have anassociated beam-width 306. In one example embodiment, there may be twodesirable targets 312 and 314 in front of the vehicle 302. A firsttarget 312 and a second target 314 may be within the beam-width 306 ofthe radar unit 310. Further, scenario 380 may include a firstundesirable target 316 and a second undesirable target 318. The secondundesirable target 318 may be within the beam-width 306 of the radarunit 310. Like previous FIGS. 3A, 3B, and 3C, for each targetidentified, a computer located within vehicle 302 may determine if eachtarget is desirable or undesirable. Additionally, based on thedetermination of the desirable and undesirable targets, the computer maydetermine the range of interest as well as an angle of interest.

As shown in scenario 380, the radar unit 310 may be able to steer theradar beam so the beam-width 306 avoids the first undesirable target318. As shown in FIG. 3D, the range of interest may have a cutoffdistance shown as cutoff limit 320. The radar system will ignore radarreflections that come from a distance greater than cutoff limit 320.Additionally, because the beam-width 306 avoids the first undesirabletarget 318, it will not contribute radar reflections. Thus, the radarsystem will ignore radar reflections from both undesirable target 316and undesirable target 318.

3. Example Methods

A method 400 is provided for operating a radar system of an autonomousvehicle in a range dwell mode. The method could be performed using anyof the apparatus shown in FIGS. 1-3D and described above; however, otherconfigurations could be used as well. FIG. 4 illustrates the blocks inan example method. However, it is understood that in other embodiments,the blocks may appear in different order and blocks could be added,subtracted, or modified. Additionally, the blocks may be performed in alinear manner (as shown) or may be performed in a parallel manner (notshown).

Block 402 includes the vehicle transmitting a first electromagneticradiation signal from a radar unit. The electromagnetic signal may takethe form of a radar signal. The vehicle described in this method couldbe the vehicle 100 and/or vehicle 200 as illustrated and described inreference to FIGS. 1 and 2, respectively. The first electromagneticradiation signal may be transmitted via one or more antennas located inthe radar unit. Further, the first electromagnetic radiation signal maybe transmitted with one of many different radar modes. However, in someembodiments it is desirable to transmit the first electromagneticradiation signal with a radar mode that allows the distance measurementof various reflecting objects in the field of view of the radar.

Block 404 includes the vehicle receiving a reflected electromagneticradiation signal at a radar unit with an array of antennas. Receivingthe reflected electromagnetic radiation signal could include receivingradio signals that are reflected from objects in the field of view ofthe radar system. A processor in the radar system may convert thereceived reflected electromagnetic radiation signals into data to relayfor further processing. For example, the radar system may transmit asignal and receive a set of reflected signals back. The radar system mayfurther identify distance and direction information to each object thatcauses reflections back to the vehicle. In some additional embodiments,the radar system may not be able to identify distance and directioninformation to each object, but rather the radar system may identifythat reflected signals come from some objects. In some instances,objects may be positioned in a way that the radar system may not be ableto identify each individual object at first. Depending upon theembodiment, the reflected signals may be processed fully or in part by aserver and communicated to the vehicle.

Block 406 includes determining a target range. In some embodiments, aprocessor within the vehicle may determine the target range. However, inother embodiments, a server may calculate the target range fully or inpart and communicate the target range to the vehicle. As previouslydescribed with respect to FIGS. 3A-3D, the target range may take severaldifferent forms. In some example embodiments, the target range may takethe form of either one of or a combination of a maximum distance, aminimum distance, a range (between a maximum distance and a minimumdistance), and an angle.

The target range may be determined based on various criteria. In oneexample, the radar reflections may indicate that there are numeroustargets in the same area. This area may be considered a target range.Additionally, there may be a large object that reflects a significantamount of radar signal. The large object (such as the object representedby target 318 in FIGS. 3A-3D) may reflect a very large radar signal andobscure reflections from smaller objects located near the large object.Therefore, the target range may be determined to be a range thatexcludes the large object. In another example, an undesirable object maybe located at an angle from the vehicle. The target range may be chosento avoid the angle of the undesirable object.

The target range may be determined based on radar reflections or oninput from other sensors. In one embodiment, a combination of vehiclesensors may be used to determine a target range. In some embodiments,the combination of sensors may not use the radar system at all. Inembodiments where the radar system is not used to determine the targetrange, blocks 402 and 404 may be omitted from method 400. However, oncethe target range is determined, the radar system may be able tointerrogate this target range.

Block 408 includes the vehicle transmitting a second electromagneticradiation signal according to a Frequency-Modulated Continuous-wave(FMCW) operating mode via one or more antennas located in the radarunit. The FMCW operating mode is a specific form of transmitting asignal with a radar unit. One of the benefits of the FMCW operating modeis the ability to resolve accurate distance and speed information fromeach signal reflection when many are present.

When operating according to FMCW operating modes, the frequency of asignal transmitted by the radar system is transmitted with both (i) afrequency-modulation and (ii) a continuous-wave form. Transmitting witha frequency-modulation means that the frequency of the transmittedsignal is varied over time. The method by which the frequency is variedcan change based on the specific embodiment. For example, the frequencycan be varied as a sine wave, a saw tooth wave, a triangle wave, orother form of frequency modulation. In one specific embodiment, theradar signal may have a base (carrier) frequency of approximately 77gigahertz (GHz). The 77 GHz base signal may be mixed with a 60 megahertzmodulation signal to produce the frequency-modulated signal. Continuouswave means that the radar signal is not sent in short bursts, but ratheris transmitted for a duration of time that is long compared to theperiod of the electromagnetic wave.

In some additional embodiments, the FMCW radar signal may also betransmitted with an associated angle. The angle may be decided based onthe target range determined at block 408. Additionally, the transmittedFMCW signal may be controlled based on the target range determined atblock 408 as well.

Although the present disclosure is generally explained in the context ofFMCW radar signals, other radar signally modes may be used within thepresent disclosure as well. For example, the present disclosure may alsobe used with stepped frequency radar, synthetic aperture radar, pulsedradar modes, and other radar modes.

Stepped frequency radar is a signaling mode in which the frequency ofthe the transmitted radar signal is increased or decreased in successivesteps. In various examples of stepped frequency radar, the transmittedradar signal may be transmitted as a continuous wave or as a series ofpulses. Further the frequency may be increased (or decreased) in alinear or non-linear steps in various examples. Step frequency radar mayenable a radar system to have an increased range resolution while havinga relatively low instantaneous bandwidth.

Synthetic aperture radar is a radar mode in which a radar signal istransmitted (usually in a plurality of pluses) by an antenna andreceived by at least one antenna at different locations for each pulse.For example, a vehicle in motion may transmit radar pluses and receiveradar reflections as the vehicle is traveling along a roadway. As pulsesare received while the vehicle is in motion, the pulses are processedtogether to obtain a higher resolution that what would be obtained witha fixed-location reception antenna. Therefore, the aperture (e.g. thearea over which signals are received) is synthetically derived based onthe motion of the vehicle.

Unlike continuous wave (CW) radar modes, pulsed radar modes transmitradar signals as pulses. For example, the radar system may repeatedlytransmit a signal for a period of time and then transmit no signal for asecond period of time. In some examples, a pulsed radar mode may alsouse the Doppler Effect (e.g. frequency shift) of received signals todetermine a velocity for the objects that cause the reflections.

Block 410 includes the vehicle receiving a second reflectedelectromagnetic radiation signal at a radar unit with an array ofantennas. Receiving the second reflected electromagnetic radiationsignal could include receiving radio signals that are reflected fromobjects in the field of view of the radar system. The second reflectedelectromagnetic radiation signal may include reflections from objectsbased on the FMCW signal transmitted at block 408. A processor in theradar system may convert the second received radar signals into data torelay for further processing. Because the signals transmitted at block408 are frequency-modulated, the second radar signal received may alsobe frequency modulated.

Block 412 includes processing the second reflected electromagneticradiation signal to only have components in associated with the targetrange. A computer that is part of the autonomous vehicle may perform theprocessing at block 412. However, in another embodiment, a computerlocated on a network (i.e. not collocated as a part of the vehicle) mayperform the processing at block 412.

The processing may be performed in several different ways. First, theprocessing may calculate the distance to each object causingreflections. In one embodiment, the time between the transmission of aspecific frequency and the reception of the same frequency can determinethe range to the object causing the reflecting. The distance to thespecific object causing the reflection is equal to half the amount oftime between transmission and reception (Δt) times the speed of light(c). The formula for the distance to a given reflector is below.

${distance} = {\frac{\Delta\; t}{2}c}$

Additionally, the distance can also be calculated by comparing thefrequency of the received signal to the frequency of the instantaneouslytransmitted signal. The distance to the reflector is equal to thedifference in the frequency of the instantaneously transmitted signaland the received signal (Δf) is divided by two times the speed of light(c) divided by the change in frequency of the transmitter per unit time

$\left( \frac{df}{dt} \right).$Thus, the range of the radar can be controlled by changing the rate ofchange of the transmission

$\left( \frac{df}{dt} \right)$from the frequency-modulation. The formula for the distance to a givenreflector is below.

${distance} = {\frac{\Delta\; f}{2}\frac{c}{\frac{df}{dt}}}$

In still yet another embodiment, the processing may include mixing thesecond reflected electromagnetic radiation signal with the secondreflected electromagnetic radiation signal with the firstelectromagnetic radiation signal. Thus, the signal received is mixedwith the signal that is being transmitted. The output of the mixing mayform a beat pattern. Each beat of the beat pattern corresponds to areflecting object at a distance that corresponds to the frequency of thebeat pattern.

These embodiments provide is the ability to select a given range forfiltering through narrow band filter located before the analog todigital converter (ADC). By filtering out returns from the undesiredranges, two benefits are achieved. The first benefit is a reduction inthe wideband noise power that is captured by the ADC due to the narrowband filter reducing the overall noise power that will be digitized. Thesecond benefit is reducing the required dynamic range to digitize thesignal of interest. If large targets are close to the system, and therange-dwell operation mode is set to process a longer range than thosetargets, the close in targets will be attenuated by the narrow bandfilter, while the desired ranges are minimally affected by the filter'sinsertion loss. This provides overall signal compression prior to theADC that does not compress the desired signal. This means that the ADC'sautomatic gain control operation will be more heavily dominated by thedesired range signal, instead of other returns in the scene.

Once the distances to the reflecting objects are calculated, thedistances can be compared to the target range. Signals that correspondto regions outside of the target range can be removed by the processingsystem. Thus, objects that produce a reflection corresponding to aregion that is not in the target region can be discarded by theprocessing system. The resulting signal would only contain signals thatare produced by objects that are located within the target range.

Block 414 includes determining at least one parameter of a targetobject. Receiving the second reflected electromagnetic radiation signalcould include receiving radio signals that are reflected from objects inthe field of view of the radar system. The second reflectedelectromagnetic radiation signal may include reflections from objectsbased on the FMCW signal transmitted at block 408. A processor in theradar system may convert the second received radar signals into data torelay for further processing. Because the signals transmitted at block408 are frequency-modulated, the second radar signal received may alsobe frequency modulated.

One difference between the range-dwell mode disclose herein andtraditional FMCW radar is that only a small set of the spectralestimation algorithm would need to be executed because the expected beatfrequencies of the targets would be known in advance. This simplifiesprocessing substantially. Using an up-chirp and a down-chirp range-dwellmode waveform can also be used with the methods and system disclosedherein to provide further information on the velocity of the targets inthe scene. This method would be similar to existing FMCW velocity/rangeestimation methods, but with the advantage of slightly altering thechirp rate to locate the beat frequencies at different spots in thenarrow band filter profile.

In one embodiment, the example computer program product 500 is providedusing a signal bearing medium 502. The signal bearing medium 502 mayinclude one or more programming instructions 504 that, when executed byone or more processors may provide functionality or portions of thefunctionality described above with respect to FIGS. 1-4. In someexamples, the signal bearing medium 502 may encompass a non-transitorycomputer-readable medium 506, such as, but not limited to, a hard diskdrive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape,memory, etc. In some implementations, the signal bearing medium 502 mayencompass a computer recordable medium 508, such as, but not limited to,memory, read/write (R/W) CDs, R/W DVDs, etc. In some implementations,the signal bearing medium 502 may encompass a communications medium 510,such as, but not limited to, a digital and/or an analog communicationmedium (e.g., a fiber optic cable, a waveguide, a wired communicationslink, a wireless communication link, etc.). Thus, for example, thesignal bearing medium 502 may be conveyed by a wireless form of thecommunications medium 510.

The one or more programming instructions 504 may be, for example,computer executable and/or logic implemented instructions. In someexamples, a computing device such as the computer system 112 of FIG. 1may be configured to provide various operations, functions, or actionsin response to the programming instructions 504 conveyed to the computersystem 112 by one or more of the computer readable medium 506, thecomputer recordable medium 508, and/or the communications medium 510.

The non-transitory computer readable medium could also be distributedamong multiple data storage elements, which could be remotely locatedfrom each other. The computing device that executes some or all of thestored instructions could be a vehicle, such as the vehicle 200illustrated in FIG. 2. Alternatively, the computing device that executessome or all of the stored instructions could be another computingdevice, such as a server.

The above detailed description describes various features and functionsof the disclosed systems, devices, and methods with reference to theaccompanying figures. While various aspects and embodiments have beendisclosed herein, other aspects and embodiments will be apparent. Thevarious aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopebeing indicated by the following claims.

What is claimed is:
 1. A method for operating a radar system comprising:transmitting a first electromagnetic radiation signal via a transceiverof a radar unit; receiving a first reflected electromagnetic radiationsignal based on the first transmitted electromagnetic radiation signalvia the transceiver of the radar unit; determining a target range via aprocessing unit based on the first reflected electromagnetic radiationsignal; transmitting a second electromagnetic radiation signal via thetransceiver of the radar unit; receiving a second reflectedelectromagnetic signal radiation based on the second transmittedelectromagnetic radiation signal via the transceiver of the radar unit;processing the received second reflected electromagnetic signal via theprocessing unit to provide a processed signal by removing components ofthe received second reflected electromagnetic signal associated withobjects outside the target range through mixing the received secondreflected electromagnetic signal with the transmitted signal and whereinthe mixing forms a range-dependent beat pattern; and determining atleast one parameter of a target object based on the processed signal,wherein the at least one parameter comprises at least one of a distanceand an angle to the target object.
 2. The method of claim 1, wherein atleast one of the first electromagnetic radiation signal and the secondelectromagnetic radiation signal comprises a signal according to asynthetic aperture radar operating mode.
 3. The method of claim 1,wherein at least one of the first electromagnetic radiation signal andthe second electromagnetic radiation signal comprises a signal accordingto a pulsed operating mode.
 4. The method of claim 1, wherein at leastone of the first electromagnetic radiation signal and the secondelectromagnetic radiation signal comprises a signal according to astepped frequency operating mode.
 5. The method of claim 1, wherein thereceiving is performed with a plurality of antennas forming an array. 6.The method of claim 1, wherein the transmitting is performed with atleast one antenna.
 7. The method of claim 1, wherein processing thereceived second reflected electromagnetic signal comprises removing aportion of the second reflected electromagnetic signal based on afrequency component of the portion of the second reflectedelectromagnetic signal, wherein the portion of the second reflectedelectromagnetic signal is removed based on: (i) the frequency componentof the portion of the second reflected electromagnetic signal, (ii) afrequency component of a portion of the second electromagnetic radiationsignal, and (iii) a time delay.
 8. A radar system comprising: an antennasystem configured to transmit and receive electromagnetic radiation; atransceiver configured to cause the antenna system to: transmit a firstelectromagnetic radiation signal; receive a first reflectedelectromagnetic signal radiation based on the first transmittedelectromagnetic radiation signal; transmit a second electromagneticradiation signal; and receive a second reflected electromagnetic signalradiation based on the second transmitted electromagnetic radiationsignal; and a processing unit configured to: determine a target rangebased on the first reflected electromagnetic radiation signal; processthe received second reflected electromagnetic signal to provide aprocessed signal by removing components of the received second reflectedelectromagnetic signal associated with objects outside the target rangethrough mixing the received second reflected electromagnetic signal withthe transmitted signal and wherein the mixing forms a range-dependentbeat pattern; and determine at least one parameter of the target objectbased on the processed signal, wherein the at least one parametercomprises at least one of a distance and an angle to the target object.9. The radar system of claim 8, wherein the transceiver is furtherconfigured to transmit at least one of the first electromagneticradiation signal and the second electromagnetic radiation signalcomprises a signal according to a synthetic aperture radar operatingmode.
 10. The radar system of claim 8, wherein the transceiver isfurther configured to transmit at least one of the first electromagneticradiation signal and the second electromagnetic radiation signalaccording to a pulsed operating mode.
 11. The radar system of claim 8,wherein the transceiver is further configured to transmit at least oneof the first electromagnetic radiation signal and the secondelectromagnetic radiation signal according to a stepped frequencyoperating mode.
 12. The radar system of claim 11, wherein at least oneantenna from the plurality of antennas transmits the firstelectromagnetic radiation signal.
 13. The radar system of claim 8,wherein the antenna system comprises a plurality of antennas forming anarray.
 14. The radar system of claim 8, wherein the processing unit isfurther configured to remove a portion of the second reflectedelectromagnetic signal based on a frequency component of the portion ofthe second reflected electromagnetic signal, wherein the portion of thesecond reflected electromagnetic signal is removed based on: (i) thefrequency component of the portion of the second reflectedelectromagnetic signal, (ii) a frequency component of a portion of thesecond electromagnetic radiation signal, and (iii) a time delay.
 15. Anarticle of manufacture including a non-transitory computer-readablemedium having stored thereon program instructions that, when executed bya processor in a radar system, cause the radar system to performoperations comprising: determining a target range; causing thetransmission of an electromagnetic radiation signal via a transceiver ofa radar unit; processing a received reflected electromagnetic signalreceived via the transceiver of the radar unit to provide a processedsignal by removing components of the received second reflectedelectromagnetic signal associated with objects outside the target rangethrough mixing the received second reflected electromagnetic signal withthe transmitted signal and wherein the mixing forms a range-dependentbeat pattern; and determining at least one parameter of the targetobject based on the processed signal, wherein the at least one parametercomprises at least one of a distance and an angle to the target object.16. The article of manufacture of claim 15, wherein processing thereceived reflected electromagnetic signal comprises removing a portionof the reflected electromagnetic signal based on a frequency componentof the portion of the reflected electromagnetic signal.
 17. The articleof manufacture of claim 16, wherein the portion of the reflectedelectromagnetic signal is removed based on: (i) the frequency componentof the portion of the reflected electromagnetic signal, (ii) a frequencycomponent of a portion of the electromagnetic radiation signal, and(iii) a time delay.
 18. The article of manufacture of claim 15, whereindetermining a target range comprises: causing the transmission of afirst electromagnetic radiation signal; processing a first reflectedelectromagnetic signal radiation based on the first transmittedelectromagnetic radiation signal.